Tris(perfluoroalkanesulfonyl)methide acid salt is a substance that is useful as a Lewis acid catalyst or ion conducting material in the fields of organic syntheses, cell electrolyte, etc. Hitherto, there have been known many of the method for producing a tris(perfluoroalkanesulfonyl)methide acid salt, which is the target of the present invention. For example, Non-patent Publication 1 discloses that a tris(perfluoroalkanesulfonyl)methide acid salt is obtained by reacting trifluoromethanesulfonyl fluoride with a methylmagnesium halide (Grignard reagent).
Furthermore, Patent Publication 1 discloses a method for obtaining a methide acid salt by conducting a reaction between a perfluoroalkanesulfonyl halide and an alkali metal methane in organic solvent.    Non-patent Publication 1: Inorg. Chem., Vol. 27, pages 2135-2137, 1988    Patent Publication 1: Japanese Patent Application Publication 2000-226392